Roger Federer welcomed the return to tennis of Rafael Nadal, but will not spend much time worrying about his long-time rival's progress as he concentrates on his own game with a Wednesday start at the Rotterdam World Tennis.
While Federer was making his preparations, there was disappointment on court for third seed Jo-Wilfried Tsonga as the French player went down to Igor Sijsling of the Netherlands 7-6 (7/3), 4-6, 6-4.
Even 14 aces could not help Tsonga in the two-hour match, with the seed converting only one of eight break point chances.
Tsonga, a finalist here in 2011, saved a match point in the final game but lost his serve a few moments later to make a surprise first-round exit.
"This is not my worst moment, but I'm disappointed," said Tsonga. "I missed four or five of the same volleys on key points. That was the difference.
"He was serving very well and I was always chasing the score. I didn't play a bad match, just missed my chances. I was missing on shots that I usually make. But I will keep working hard and try to improve things."
Tsonga's s compatriot the fifth seeded Gilles Simon moved into the second round with a 7-6 (7/3), 6-4 victory over German qualifier Daniel Brands.
Romanian Victor Hanescu accounted for the week's first seed with his defeat of seventh-seeded Jerzy Janowicz 7-6 (7/4) 6-3. The Pole had made a breakthrough last autumn at Paris Bercy by reaching the final after coming through qualifying.
Grigor Dimitrov ended a four-match losing streak with a win over Australian Bernard Tomic 6-3, 3-6, 6-3.
Top seed Federer, defending his 2012 trophy said he has arrived relaxed and eager as he plays for the first time since losing a tight Australian Open semi-final to Andy Murray, then taking time off with his family in his homes in Dubai and Switzerland.